Aerosol lubricating device, lubricating arrangement and lubricating method

ABSTRACT

There is provided a lubricating device for a device to be lubricated having at least two friction members, wherein the lubricating device includes producing an oxygen-free aerosol of a liquid lubricant in a carrier fluid, and supplying the aerosol to the device to be lubricated. A method is also provided.

BACKGROUND

The present invention pertains to an aerosol lubricating device, anarrangement with such a lubricating device, as well as a correspondinglubricating method.

The lubrication of machine elements with lubricants such as differenttypes of grease, oil or solid lubricant fulfills different functions. Onthe one hand, it serves for preventing or reducing wear phenomena atcontact points between so-called friction partners, for diminishingstress concentrations, for example, in rolling bearings and for reducingadditional frictional shearing stresses on surfaces. Lubricants arefurthermore used for corrosion protection and also for cooling machineelements if a sufficient lubricant exchange and therefore acorresponding dissipation of heat can be ensured.

The objective of lubrication consists of separating contacting surfacesof the friction partners by means of a hydrodynamic liquid film or aprotective reaction layer. In the hydrodynamic formation of lubricatingfilms, an elastic deformation frequently also plays an important rolesuch that one refers to so-called elastohydrodynamic lubrication in thiscase. The main objective of lubrication is a complete separation of thefriction partners. This can be achieved with a suitable combination ofthe lubricant viscosity, the moving speed of the friction partners andthe contact pressure, as well as corresponding constructive adaptations.

As mentioned above, different types of lubricating oil, lubricatinggrease and solid lubricant are used as lubricants. This applicationmainly focuses on liquid lubricants such as, e.g., lubricating oils.Important parameters of lubricating oils that can be influenced are thedensity, the viscosity index, the shear stability, the so-calledCloud-and-Pour point, the neutralization capacity, the neutralizationvalue, the total base number and the flash point. Furthermore, thethermal capacity, the air absorption capacity and the content of waterand foreign matter influence the properties of lubricating oil.

Various types of lubricant additives are known for modifyingtribologically relevant lubricating oil properties, for example, theviscosity/temperature behavior and/or the frictional and wear behavior,as well as for improving the oxidation resistance or the prevention offoaming.

Additives may be added to lubricating oil in the form of commerciallyavailable so-called additive packets. In modern motor oils, 10 to 20% ofthe overall volume consists of additives. Polymeric additives typicallyform another 3% of the overall volume.

The service life of lubricating oils is limited. Due to interactionswith the system to be lubricated and the surrounding atmosphere, theservice life of the lubricating oil and of the entire tribologicalsystem can be significantly reduced. In this context, oxidationprocesses that lead to an increase of the neutralization value andtherefore an increased corrosiveness of the lubricating oil areconsidered particularly critical. An increase of the viscosity causesthe tribological properties of the system to change over time. Depositsformed due to corrosion by separating lubricating oil components cancause blockages. A loss of additives can result in certain components ofthe lubricating oil no longer being sufficiently protected such that itsquality deteriorates. Consequently, frequent oil changes or maintenanceintervals are required.

It would therefore be desirable to increase the service life of alubricating oil or, more generally, a liquid lubricant, particularly alubricating oil that is based on minimal oil.

SUMMARY OF THE INVENTION

Based on these circumstances, the present invention proposes an aerosollubricating device for a device to be lubricated with at least twofriction partners, an arrangement with such a lubricating device, aswell as a corresponding lubricating method.

The invention proposes a lubricating device that can be coupled with adevice to be lubricated and comprises means for producing an oxygen-freeaerosol of a liquid lubricant (e.g., a lubricating oil) in a carrierfluid, as well as means for supplying the correspondingly producedaerosol to the device to be lubricated. The preferred carrier fluid usedis gaseous and contains no oxygen. The carrier fluid preferably is alsofree of other corrosive components, particularly water and abradantparticles.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows a lubricating arrangement according to an embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

Although the present invention refers to an “oxygen-free” aerosol or an“oxygen-free” carrier fluid, these terms also include an aerosol orcarrier fluid that still has slight (residual) contents of dissolvedoxygen or is able to produce slight amounts of oxygen. Although it isdesirable that the lubricant protection gas is completely oxygen-free,this is usually associated with significant additional costs.

Methods for removing oxygen, for example, from corresponding gases aresufficiently known. For example, oxygen can be condensed out of air in acooling trap or catalytically separated. Inert gases such as argon,nitrogen or carbon dioxide may also be provided in liquid, oxygen-freeform and transferred into the gaseous phase prior to the utilization ina lubricant protection gas.

The inventive measures make it possible to create an oxygen-freelubricant/gas system in a device to be lubricated that is permanentlyavailable in said device and significantly prolongs the service life offrictional components. Consequently, the maintenance intervals ofcorresponding systems can be significantly extended such that higheravailability and/or lower maintenance costs are achieved. Due to acorresponding oxygen-free lubricant atmosphere, it is also possible toutilize oxygen-sensitive lubricant additives without having to carry outa frequent lubricant change.

The lubricating device may include means for producing an oxygen-freeaerosol in the form of a lubricant reservoir and a feed device that isarranged in the lubricant reservoir and serves for introducing thecarrier fluid into the lubricant. The feed device may consist, forexample, of a gas bubbling device that makes it possible to produce gasbubbles that flow through the lubricant and during this process producean aerosol and/or a lubricant mist. The gas bubbles may be produced, forexample, by a filter (membrane or frit), wherein the gas bubble size isinfluenced with the respective pore size. The introduction of thecarrier fluid and therefore the production of the aerosol may take placecontinuously or intermittently, e.g., in lubricating intervals.

Typical gas throughputs lie, for example, in the range between 1 literand 20 standard cubic meters per second.

In the context of the present invention, an “aerosol” refers to anysystem, in which a liquid lubricant is present in a gaseous carrierfluid, e.g., in the form of droplets. The respective droplet size maysignificantly vary in this case and lie in the range between 0.5 nm andseveral 10 μm.

A corresponding lubricating arrangement includes a device to belubricated with at least two friction partners and a lubricating deviceof the above-described type. The lubricating device is provided withmeans for supplying the aerosol to the device to be lubricated in thiscase. The device to be lubricated and the lubricating device areconnected to one another by a gas-tight channel. Due to the coupling ofthe lubricating device to the device to be lubricated, a closed systemis created such that the admission of oxygen into the lubricatingarrangement can be prevented.

A corresponding lubricating arrangement includes a device to belubricated that is designed for the flow-through of the oxygen-freeaerosol. In this way, a lubricant atmosphere or an oxygen-free aerosolcan be continuously or intermittently regenerated in the device to belubricated such that a particularly effective protection is achieved.

For this purpose, the device to be lubricated features outlet openingsfor liquid lubricant, aerosol and/or gas. A separating device for liquidlubricant and corresponding outlet openings may be provided for removinglubricant separated from the aerosol, e.g. due to condensation, from thedevice to be lubricated. The removed liquid lubricant can then besubjected, for example, to a cleaning process (e.g. by means offiltration or chemical processing) and/or once again supplied to alubricating device. Gas that no longer contains any lubricant componentscan be removed from the system in the same fashion. It would also bepossible for the aerosol to continuously flow through the device to belubricated and to further treat the aerosol in a separating device. Forexample, liquid lubricant can be separated in a separating device andonce again supplied to an inventive lubricating device as describedabove.

A lubricating arrangement may also be provided that includes a heatingdevice for the carrier fluid, the lubricant and/or the aerosol. It isgenerally known that certain heated gases such as, for example,acetylene or carbon monoxide positively influence the tribologicalproperties of a system to be lubricated. It would therefore be possibleto provide a correspondingly heated gas flow by means of a gas heater.Corresponding heating devices ensure that parameters of the lubricantand/or the aerosol such as, for example, its density, its viscosityand/or its compressibility can be controlled particularly well.

At an elevated temperature in the lubricating device, it would bepossible, if applicable, to make available a larger quantity oflubricant in the aerosol. If heated aerosol is introduced into a (cool)gearing, liquid aerosol particles are deposited on the respectivecomponents due to condensation such that a very good and purposefullubrication can be achieved.

In this case, the heating may take place in the lubricating device, aswell as in the device to be lubricated, wherein a gas flow, a lubricantand/or the obtained aerosol can be selectively heated.

An inventive lubricating method includes the production of anoxygen-free aerosol by utilizing the above-described lubricating device.

In a corresponding method, inert gases such as argon or nitrogen, aswell as gases such as carbon dioxide, carbon monoxide and/or acetylenethat are known to positively influence the tribological properties of asystem to be lubricated may be used as carrier fluid. Corresponding gasmixtures may also be utilized.

The lubricant used consists of a lubricant that is based on mineral oil,particularly a mineral oil with polymeric additives and/or additives. Asalready mentioned above, the improved protection of the lubricantachieved with the inventive measures also makes it possible to utilizepolymeric additives that could not be used in conventional lubricatingsystems so far because they would have been subjected to the damagingoxidation effect of oxygen. However, the utilization of the inventionalso makes it possible, in particular, to eliminate certain additivessuch as, e.g., antioxidants such that significant cost advantages can berealized.

As mentioned above, a certain viscosity, density and/or compressibilityof the lubricant and/or the aerosol can be adjusted in a correspondingmethod. This can be realized, for example, with a suitable gascomposition and gas temperature and/or a suitable flow speed or withcorrespondingly adjusted pressures.

The inventive method can be utilized in the number of devices to belubricated such as, for example, turbines of wind power plants, engineparts, bearings, valves and valve drives, as well as cutting tools.

Other advantages and embodiments of the invention result from thedescription and the attached drawing Figure.

The characteristics described above and below can be used in therespectively described combination, and also in other combinations orindividually without deviating from the scope of the present invention.

An exemplary embodiment of the invention is schematically illustratedand described in greater detail below with reference to the drawingFigure.

A lubricating arrangement or system according to an embodiment of theinvention is illustrated in the Figure and altogether identified by thereference symbol 100. The lubricating arrangement 100 comprises alubricating device 10 and a device 20 to be lubricated. The lubricatingdevice 10 features means 11 for producing an oxygen-free lubricantaerosol with a reservoir 13 for liquid lubricant and a feed device 14that is arranged in the reservoir 13 and serves for introducing acarrier fluid into the lubricant. The feed device 14 includes a supplyline 15 for the carrier fluid (gas) and on its other end preferably amembrane and/or a frit, by means of which gas bubbles can be produced inthe lubricant.

Means 12 are provided for transferring the aerosol produced by means ofbubbling in the lubricating device into the device 20 to be lubricated.

The device 20 to be lubricated includes at least two friction partners21, 22 or members that are symbolized in the form of toothed wheels anddriven by motors M1 and M2. The friction partners 21, 22 areaccommodated in a housing 23 that is at least partially gas-tight andrealized such that an inflowing aerosol is present in the housing 23 ina controlled quantity and/or this aerosol can flow through the housingwith a controlled speed. On its bottom side, the housing 23 may beprovided with outlet openings 24 for liquid lubricant in order to ensurethe removal of lubricant 26 condensed out of the aerosol. Outletopenings 25 for aerosol and/or gas may be provided at a differentlocation, e.g., on the cover side of the housing 23.

The device 20 to be lubricated may also be selectively realized for oilbath lubrication, wherein a lubricant sump may be at least partiallyformed or supplied by the lubricant 26 condensed out of the aerosol.

What is claimed is:
 1. A lubricating device (10) for a device (20) to belubricated having at least two friction members (21, 22), comprisingmeans (11) for producing an oxygen-free aerosol comprising a liquidlubricant and a carrier fluid, and means (12) for supplying the aerosolto the device to be lubricated, the supplying means coupled to and incommunication with the device to be lubricated.
 2. The lubricatingdevice (10) according to claim 1, wherein the producing means comprisesa lubricant reservoir (13) for the liquid lubricant and a feed device(14) arranged in the lubricant reservoir for introducing the carrierfluid into the lubricant.
 3. A lubricating system (100), comprising adevice (20) to be lubricated with at least two friction members (21,22), and a lubricating device (10) coupled to and in communication withthe device to be lubricated.
 4. The system (100) according to claim 3,wherein the device (20) to be lubricated is constructed and arranged fora flow-through of an oxygen-free aerosol.
 5. The system (100) accordingto claim 4, wherein the device (20) to be lubricated comprises outletopenings for release of any of the liquid lubricant, oxygen-free aerosoland gas.
 6. A method for lubricating a device (20) with at least twofriction members (21, 22), comprising producing an oxygen-free aerosolincluding a liquid lubricant produced in a carrier fluid, and supplyingthe aerosol to the device.
 7. The method according to claim 6, whereinthe carrier fluid is selected from the group consisting of argon,nitrogen, carbon dioxide, carbon monoxide, and acetylene.
 8. The methodaccording to claim 6, wherein the liquid lubricant comprises a lubricantwith an oil therein selected from the group consisting of mineral oil,mineral oil with polymeric additives, mineral oil with additives, andmineral oil with polymeric and other additives.
 9. The method accordingto claim 6, further comprising adjusting characteristics of at least oneof the liquid lubricant and the oxygen-free aerosol, the characteristicsselected from the group consisting of temperature, viscosity, densityand compressibility of the liquid lubricant and the oxygen-free aerosol.10. The method according to claim 6, further comprising heating any ofthe liquid lubricant, the oxygen-free aerosol, and the carrier fluid forthe oxygen-free aerosol.